I have installed Zammad and tried it with a few users. People have asked me how to reply to tickets, because the UI is confusing. I also struggled with this for the first time I replied to a ticket.
The “Update” button at the bottom is not an obvious corresponding action to “Reply”, specially on other languages/translations such as spanish and portuguese.
I could not find a config to change that and make it so we can have a “Reply” button right after the text editor. This is the reason I suggest adding an option for that button or offer users two different “views” for the ticket page, so they can choose between the current “modern” or a new “classic” view that contains a reply button. This could be a global setting or even something added to the user profile.
Related discussion: User-friendliness & usability analysis and suggestions